Operation

OPERATION

The washer fluid level switch uses fluid conductivity to monitor the level of the washer fluid in the washer reservoir. Electricity is conducted between the two switch pins or electrodes only when they are immersed in the washer fluid, which closes the switch circuit. When the fluid level in the washer reservoir falls below the pins, electrical current cannot be conducted and the switch becomes an open circuit, which signals a low fluid condition. The switch is connected in series between a sensor return circuit and the washer fluid switch sense input to the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM).

In order to prevent decomposition of the switch electrodes, the switch receives an alternating current from the BCM. The BCM monitors the switch return signals and is programmed to respond to open switch circuit readings by sending an electronic washer fluid indicator lamp-ON message to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN or KOMBIE) over the Controller Area Network (CAN) data bus. The EMIC responds to this message by illuminating the washer fluid indicator.

The washer fluid level switch and the hard wired circuits between the switch and the BCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the washer fluid level switch or the electronic controls or communication between other modules and devices that provide some features of the wiper and washer systems. The most reliable, efficient, and accurate means to diagnose the washer fluid level switch or the electronic controls and communication related to washer fluid level switch operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.